1. Field of the Invention
The present invention relates to an apparatus for measuring a thickness of a powder deposited on an inner surface of a pipe, and more particularly, to an apparatus which is capable of more precisely measuring a thickness of a dielectric powder deposited on an inner surface of a pipe by identifying a kind of the dielectric powder deposited in the pipe.
2. Discussion of Related Art
In a pipe or the like connected to a vacuum chamber for producing a semiconductor, an LCD, an LED, an MEMS or the like, the inside of which should be evacuated, or from which gas should be continuously discharged, the gas includes fine powder, and the powder is deposited on an inner surface of the pipe during the continuous discharge operation. The deposited powder decreases a diameter of the pipe, which in turn causes the discharge operation to take a longer period of time, and/or a backflow phenomenon. Such backflow phenomenon may result in, for example, a damage of a wafer or a fire outbreak.
There has been an effort to inhibit such a problem, periodically replacing a pipe and applying heat from an outside to a pipe so as to delay a deposition cycle. On the other hand, an apparatus for measuring a thickness of a powder deposited on an inner surface of a pipe has been developed.
An example of such apparatus has been disclosed in Korean Patent No. 10-1221619. The conventional apparatus described herein includes one or more electrode parts having an electric charge surface corresponding to a partial shape of an inner circumstantial surface of a pipe, and a capacitance measuring part conductively connected with the electrode parts and configured to measure a capacitance. A method of measuring a thickness of a powder deposited on an inner surface of a pipe with the conventional apparatus configured as above-mentioned is as follows. That is, first the conventional apparatus is installed at a clean pipe in which the powder is not deposited, and the capacitance is measured. This capacitance is set as a reference value. Then, the pipes in which a powder has been deposited on the inner surface thereof are collected, and thicknesses of the powder are measured. After that, the conventional apparatus is installed at each of the collected pipes to measure capacitances, and thus obtained capacitances are set as comparison values. Next, the reference value and the comparison values are stored in a database, and the conventional apparatus is installed at a pipe to be inspected, and measures a capacitance to obtain a thickness of the powder deposited in the inner surface of the pipe.
However, if the conventional apparatus is installed in a pipe in which a different kind of powder from the powder corresponding to the reference value and comparison values stored in the database is deposited, the conventional apparatus may provide inaccurate information regarding a thickness of the powder deposited on the inner surface of the pipe. In other words, since a different kind of a powder has a different relative dielectric constant, if the reference value and the comparison values obtained from a different kind of powder are used to obtain the thickness of a powder deposited on an inner surface of a pipe, the conventional apparatus may provide inaccurate thickness information.